Vibrating fluid sensors, such as Coriolis mass flow meters and vibrating densitometers typically operate by detecting motion of a vibrating conduit that contains a flowing material. Properties associated with the fluid in the conduit, such as mass flow, density and the like, can be determined by processing measurement signals received from motion transducers associated with the conduit. The vibration modes of the vibrating material-filled system generally are affected by the combined mass, stiffness, and damping characteristics of the containing conduit and the material contained therein.
A typical vibrating fluid meter includes one or more fluid conduits that are connected inline in a pipeline or other transport system and convey material, e.g., fluids, slurries and the like, in the system. Each conduit may be viewed as having a set of natural vibration modes, including for example, simple bending, torsional, radial, and coupled modes. In a typical Coriolis mass flow measurement application, a conduit is excited in one or more vibration modes as a material flows through the conduit, and motion of the conduit is measured at points spaced along the conduit. Excitation is typically provided by an actuator, e.g., an electromechanical device, such as a voice coil-type driver, that perturbs the conduit in a periodic fashion. Mass flow rate may be determined by measuring time delay or phase differences between motions at the transducer locations. Two such transducers (or pick-off sensors) are typically employed in order to measure a vibrational response of the flow conduit or conduits, and are typically located at positions upstream and downstream of the actuator. The two pickoff sensors are connected to electronic instrumentation by cabling, such as by two independent pairs of wires. The instrumentation receives signals from the two pickoff sensors and processes the signals in order to derive a mass flow rate measurement.
One type of vibrating meter uses a single loop, serial path flow conduit to measure mass flow. However, the use of a single loop, serial path flow conduit design has an inherent disadvantage in that it is unbalanced and may be affected by external vibrations to a greater extent than other types of meters. A single loop, serial flow Coriolis flow meter has a single curved conduit or loop extending in cantilever fashion from a solid mount. The flow meter must include a rigid structure positioned next to the flow conduit against which the flow conduit can vibrate. The use of the rigid structure can be impractical in many industrial applications.
Another prior art approach uses a dual loop, parallel flow conduit configuration. Dual loop, parallel flow conduit flow meters are balanced and changes in density affect both of the parallel flow conduits substantially evenly. The parallel flow conduits are driven to oscillate in opposition to one another with the vibrating force of one flow conduit canceling out the vibrating forces of the other flow conduit. Therefore, in many applications, a dual loop parallel flow conduit configuration is desirable. However, because the flow is split between two parallel flow conduits, each of the flow conduits is smaller than the connected pipeline. This can be problematic for low flow applications. Specifically, the smaller flow conduits required in dual loop, parallel flow conduit flow meters are more prone to plugging and the manifold used to split the flow between the flow conduits results in a higher pressure drop.
The above mentioned problems can be solved by using a dual loop, serial flow path flow meter. The dual loop, serial flow path flow meter combines the advantages of the single loop flow meter and the dual loop, parallel path flow meter.
FIG. 1 shows a portion of a prior art dual loop, serial flow path flow meter 100. The flow meter 100 is shown and described in more detail in U.S. Pat. No. 6,332,367, assigned on its face to the present applicants, and incorporated herein by reference for all that it teaches. The flow meter 100 includes a single flow conduit 101, which is contained within a housing 102. The flow conduit 101 includes two loops 103, 104, which lie in planes that are parallel to one another. The loops 103, 104 vibrate in response to a signal applied by the driver 110. Pick-offs 111, 111′ can detect the motion of the loops 103, 104 to determine various fluid characteristics. The loops 103, 104 are joined together with a crossover section 105. The crossover section 105 joins the two loops to form the continuous flow conduit 101. The crossover section 105 along with the two loops 103, 104 are connected and secured using an anchor 106. Although the anchor 106 is coupled to the housing 102 using pins 107, external vibrations are still experienced by the vibrating portion of the flow conduit 101 (above the brace bars 108, 109). Further, as shown, the crossover section 105 simply hangs freely and is not supported in any manner. As the length of the crossover section 105 increases, the lack of support can become problematic and result in erroneous measurements as the crossover section 105 can be subjected to distortions.
Therefore, while the prior art dual loop, serial flow path flow meter 100 provides an adequate flow meter in some situations, there is still a need to further limit external vibrations experienced by the pick-offs as well as provide a better support for the crossover section. The embodiments described below overcome these and other problems and an advance in the art is provided. The embodiments described below provide a dual loop, serial flow path flow meter mounted on a one-piece conduit support. The one-piece conduit support can adequately support the conduit's crossover section while minimizing external vibrations experienced by the flow conduit's pick-offs. Therefore, more accurate flow rates can be determined in more diverse environments.